This invention relates generally to the preparation and use of thermal shields for engine components. More particularly, the invention relates to compositions of purely metallic layers for such purposes.
Internal combustion engines become more efficient as piston face skin temperatures become higher. A thermal shield will permit considerably higher face skin temperatures without failure of a piston head than otherwise possible under conventional practices.
Numerous prior art composite thermal shields have been suggested, but few have realized practical success. Most have included an exposed ceramic layer employed in combination with adjoining underlying layers of other thermally insulative materials such as metallic insulation. Typically, the ceramic layers are applied to the metallic layers by electrostatic deposition techniques, and more popularly via plasma spray. A principal drawback of prior art ceramic composites as utilized with metallic layers has been the difficulty of adherence of ceramics to metallic materials. In fact, many of the failures of ceramics are attributable to bonding agents employed to create durable adherence of ceramics to metals. Often, the ceramics are subject to either catastrophically breaking apart, or gradually flaking away under the severe conditions of combustion.